SOLUTION: How would you apply a factoring formula to completely factor the expression x^4 - 81?

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Question 421903: How would you apply a factoring formula to completely factor the expression x^4 - 81?
Answer by richard1234(7193) About Me  (Show Source):
You can put this solution on YOUR website!
Apply the difference of two squares, rewriting x%5E4 as %28x%5E2%29%5E2 to obtain

%28x%5E2+-+9%29%28x%5E2+%2B+9%29 We can apply the formula again to obtain

%28x%2B3%29%28x-3%29%28x%5E2+%2B+9%29

x%5E2+%2B+9 cannot be factored over the real numbers, so we leave it in this form.